Nasal masks currently are employed for various purposes, including the delivery of oxygen to persons who suffer from lung disease or who are exposed to rarefied atmospheres, for administering anesthetic gases and for delivering pressurized air to persons who suffer from disorders such as sleep apnea. The masks usually are molded from a relatively soft, resilient, elastic material and they are shaped during manufacture to match the facial contours of an average intended wearer. However, a problem with the known types of masks is that, because individuals vary so much from the average, the masks must be forced against their inherent resiliency to deform and so adapt to the shapes of the users in order to avoid gas leakage. This requires that the masks be secured firmly by retaining straps or harnesses in order to prevent air leakage.
Flow generators are typically utilized to deliver a breathable gas to a patient wearing a mask. The flow generator is generally connected to flexible tubing which is secured to a mask worn by a patient. If the flow generator's operation is interrupted as a result of a power outage or other mechanical or electrical failure, there may be a significant build up of carbon dioxide in the mask as the patients exhaled air is not washed out of outlet vents which are usually contained in the mask. This may present a health problem to the patient. Additionally, when oxygen is being delivered in a closed system by a flow generator, and there is a failure of the flow generator, oxygen may still be delivered. If and when power is restored to the flow generator, there may be a significant amount of oxygen present in the flow generator creating a possible explosion hazard. Finally, there are often humidifiers used with flow generators. Any water from the humidifier should be prevented from entering the generator.
There have been numerous patents which have addressed some sort of safety valve for gas or air delivery masks. An example of such a patent is U.S. Pat. No. 5,438,981. This patent utilizes a counter balanced, rigid valve element which depending on the gas flow, either covers an opening to the ambient air or covers the gas flow airway such that the air or breathing gas is forced out into the ambient air opening. However, this system suffers from being a fairly complicated and expensive system which must rely on a counter balanced moving part. Additionally, if any condensation from the air gets on or around the balanced valve element, the operation of this valve element may be compromised. Finally, this valve is difficult to clean.
Thus, there is a need for a valve with fewer moving parts and easier operation in the event of moisture or condensation entering the valve element.